DESCRIPTION: Visual selective attention is a powerful cognitive brain mechanism that enables the processing of relevant stimuli while minimizing interference from irrelevant and/or distracting events. An overall goal of the research proposed here is to elucidate the time course and functional anatomy of attentional processes in order to test current models of visual attention. In parallel with behavioral and psychophysical measures, event-related potentials (ERPs) will be used to provide measures of neural activity related to discrete stages of stimulus processing, as well as that related to the top-down executive control of attention. Functional magnetic resonance imaging (fMRI) will be employed to identify the neuroanatomical systems and circuits involved in specific attentional processes. This proposal has six specific aims: (1) to investigate the mechanisms of spatial attention in modulating incoming signals at early stages of visual cortical processing, (2) to investigate the neural mechanisms of space, feature and object-based attention and how these interact in normal perception, (3) to investigate the role of attention in biasing competitive interactions among stimuli in multiple visual areas, (4) to investigate pretarget attention-related changes in background activity in visual cortex via top-down control processes and their relationship to attentional modulation of target-evoked activity, (5) to investigate the neural systems and circuits that mediate top-down (voluntary) attentional control during spatial versus non-spatial orienting, and (6) to investigate the neural mechanisms of top-down attentional control for global versus local attention. Throughout the proposed research, the combined use of ERPs and fMRI will provide complementary measures of the time course and functional anatomy of attentional mechanisms. Because selective attention is an essential cognitive process, elucidating basic attention mechanisms in humans remains a high priority in the effort to understand, diagnose and treat psychological and psychiatric conditions that involve deficits in attention.